The relation of optics, light, and fusion is simple. Optics is the branch of
Physics that deals with light and vision. Lasers are used by NIF  for fusion to occur. Laser is (l)ight (a)mplification by (s)timulated (e)mission of (r)adiation.
Lasers are used for extreme heat for fusion to occur. Nuclear fusion occurs, hydrogen atoms fuse to form helium and also releases energy in the form of neutrons and x-rays.
 Though it is costly, I am optimistic about the potential benefits of the project.
It is not proven that the world will be dead in the next few years, therefore i think the long term benefits will exceed the money being used for development in present time. This project is to better use energy and for better living.